The present invention relates to a method for electrolytically producing compound workpieces such as have coating layers and/or which constitute shaped components. The non-soluable foreign or extraneous material is contained in the electrolyte in a uniform distribution and is deposited together with the metal component. The extraneous material may be particles within a wide range of particle sizes.
Methods of this type are well known in the art for producing layers and shaped parts having a metal matrix in which the solid particles of the extraneous material are embedded in the form of a powder or in the form of fibers. Such deposits are used to provide wear resistant coatings, dry lubrication films, as well as hardenable metal alloys capable of being tempered, for example, to be used as control elements, for instance, in nuclear technology and similar uses.
In performing such electrolytic processes it is essential for the deposition that one obtains a homogeneous compound material in which the particles are uniformly distributed in a defined manner. In order to achieve this, it is necessary that the particles are evenly distributed already in the electrolyte.
Prior art methods for maintaining the particles in suspension in the electrolyte comprise keeping the electrolytic bath in motion, either by air under pressure or by mechanical means. However, this type of keeping the electrolytic bath in motion is not satisfactory for assuring a uniform distribution of the particles in the electrolyte and thus in the matrix to be established. In fact, the distribution is rather non-uniform and it is difficult to control the particle distribution throughout the electrolytic bath.
Another disadvantage in prior art methods for keeping the bath in motion is seen in that the bath motion disturbs the electrolytic processes. Besides, it is not possible to increase the particle density in the bath to the extent desired since it is not possible to keep the particles in suspension where the particle density is high. Thus, the particle distribution becomes even more random. Yet another disadvantage of prior art methods is seen in that the particle size is limited because larger particles tend to sink faster than small particles. Thus, it is necessary to increase the bath motion to the possible limits even where the particles have a size within the range of a mere 3 to 5 microns.
U.S. Pat. No. 3,379,634 discloses an apparatus for performing an electrolysis at zero gravity for the purpose of generating oxygen and hydrogen from an aqueous electrolyte solution. The known apparatus, although suitable for producing gases, for example, in outer space, does not provide any teaching for producing of workpieces by electrolytic deposition.
U.S. Pat. No. 3,061,525 discloses an electrolytic plating method and apparatus which is not suitable for use in outer space because it employs the above mentioned disadvantages of keeping the electrolyte in motion by various mechanical means, whereby it is difficult to sustain a uniform suspension of the particles in the electrolyte liquid. Besides, this known method is limited to smaller particle sizes ranging from sub-micron particles sizes to sizes of up to about 20 mesh.
British Pat. No. 1,218,179 also describes the production of electro-deposited coatings under gravity conditions, whereby the electrolytic bath container has a downwardly tapering bottom which is supposed to facilitate a strong upward flow in the bath. The upward flow is supposed to counteract the gravity. However, no uniform flow distribution and hence no uniform particle distribution throughout the electrolytic bath is possible in accordance with this type of known apparatus. Thus, the just described prior art devices are not suitable for producing high strength composite materials or rather, workpieces of such materials which must meet high performance standards. Such standards can only be met if the materials or workpieces have a maximum homogenity throughout their volume. Such high homogenity is, for example, necessary in turbine vanes of propulsion systems.